Optical system and optical apparatus including the same

Abstract

An optical system in which a maximum value of a height from an optical axis of a paraxial marginal ray closer to an expanded side than a point of intersection between an optical axis and a paraxial chief ray, includes a lens unit Lr including at least one refractive optical element Gn of a negative refractive power. In the optical system, νd (Gn) as an Abbe number of a material of the refractive optical element Gn, θgF (Gn) as a partial dispersion ratio regarding g and F-lines, FGn as a focal lengths of the refractive optical element Gn, and Fr as focal lengths of the lens unit Lr are set appropriately.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an optical system and an optical apparatus including the same, for example, an optical apparatus such as a silver film camera, a digital still camera, a video camera, a telescope, a binocular, a projector, or a copying machine.[0003]2. Description of the Related Art[0004]The optical system used for the optical apparatus such as a digital camera or a video camera has to be short in total lens length (total optical system length: length from first lens surface of object side to image surface), and small in overall size.[0005]Generally, as the optical system is smaller, more aberrations, in particular chromatic aberrations such as on-axis chromatic aberrations or magnification chromatic aberrations occur, to reduce optical performance.[0006]In the optical system of a telephoto type (telephotographic) where a total lens length is shortened, in particular, more chromatic aberrations occur as ...

AI Technical Summary

Benefits of technology

[0023]The present invention provides an optical system which can correct various aberrations such as chromatic aberrations well, has a compact structure as a whole, and exhibits high optical performance, and an optical apparatus including the optical system.

Problems solved by technology

Generally, as the optical system is smaller, more aberrations, in particular chromatic aberrations such as on-axis chromatic aberrations or magnification chromatic aberrations occur, to reduce optical performance.

An image-taking optical system of a telephoto type having a long focal length is generally large in size, and heavy in weight.

Thus, it is mechanically difficult to perform focusing by using the entire image-taking optical system.

However, in a lens made of a low-dispersed glass such as a fluorite having a large Abbe number, when a refractive power is increased to correct chromatic aberrations, aberrations other than the chromatic aberrations, such as spherical aberrations, coma aberrations, or astigmatism occur by a large number.

However, the increased number of lenses leads to enlargement of the entire optical system and an increase in weight.

A glass material such as a fluorite having abnormal partial dispersion characteristics can not be repeatedly used because the processing is extremely difficult and a surface can be easily damaged.

Inappropriate setting of such conditions leads to a difficulty of obtaining high optical performance by miniaturizing the entire optical system and correcting chromatic aberrations well.

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